1. Field of the Invention
This invention relates generally to communications systems, and, more particularly, to a method and apparatus for configuring a voice over internet protocol (VOIP) client connection.
2. Description of the Related Art
Public switched telephone networks have been used for many years for voice communication. A typical telephone converts sound waves into analog signals, which are then transmitted through the public switched telephone network (PSTN) to another telephone which converts the analog audio signals back into sound waves. In recent years, wireless and cellular telephones have been rising in popularity, due to their mobility. Users are no longer tied to a stationary telephone, but are free to carry their telephones with them.
Increasingly, users are using mobile devices for data transfer, as well as for voice communication. Portable digital devices have been developed that facilitate both data and voice communication over a network. Such voice communication is commonly referred to as voice over internet protocol (VOIP) communication. Voice data is compressed into packets and delivered to the destination in a manner that is similar to the handling of data packets.
There are various types of networks to which connectivity may be desired. For example, a mobile device may connect over a network to establish voice connections with the PSTN. However, many businesses are equipped with private branch exchange (PBX) or private automatic branch exchange (PABX) systems to handle internal communication. A PBX system allows a certain number of direct lines (e.g., connections to the PSTN) to be distributed to other telephones via the use of extensions. For example a business may install a PBX system and have 5 direct lines coming into the business. Through the PBX, the five lines may be linked to 20 telephones to the system using extension lines. Calls within the business may be transferred and lines may be linked for teleconferencing. Typically, a PBX system also allows for other features such as call forwarding, call diversion, etc. While networks such as the PSTN are heavily governed by standards to insure consistency, PBX systems have no such oversight or consistency. Each PBX manufacturer typically has its own proprietary codes for performing functions such as call forwarding, transferring, etc.
Systems implementing a wide area network (WAN) using wireless data communications techniques have been generally available for many years. Implementations exist which employ radio-frequency (RF) communication systems and frequency-modulated (FM) radio communications. Frequency-modulated communication techniques include both conventional point-to-point radio and broadcast. These systems include RAM Mobile Data Service using the Mobitex protocol; the Advanced Radio Data Information Service (ARDIS), manufactured by ARDIS Company, Lincolnshire, Ill.; and the Cellular Digital Packet Data (CDPD) service.
Wireless local area networks (WLANs) are used in a variety of business and other settings. Wireless local area networks use infrared or radio frequency communications channels to communicate between stationary, portable, or mobile computer units and stationary access points or base stations. These access points are in turn connected by a wired or wireless communication channel to a network infrastructure which connects groups of access points together to form a local area network, including, optionally, one or more host computer systems.
Wireless infrared and radio frequency (RF) protocols are known which support the logical interconnection of mobile devices having a variety of types of communication capabilities to host computers. The logical interconnections are based upon an infrastructure in which at least some of the remote terminals are capable of communicating with at least two of the access points when located within a predetermined range therefrom, each terminal unit being normally associated with and in communication with a single one of such access points. Based on the overall spatial layout, response time, and loading requirements of the network, different networking schemes and communication protocols have been designed so as to most efficiently regulate the association of the mobile unit with specific access points, and the availability of the communication channel to individual mobile units for broadcasting.
One such protocol is described in U.S. Pat. Nos. 5,029,183; 5,142,550; 5,280,498; and 5,668,803 each assigned to Symbol Technologies, Inc. and incorporated herein by reference. Another such protocol is described in U.S. Pat. No. 5,673,031. Still another protocol is set forth in the IEEE Standard 802.11 entitled “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications” available from the IEEE Standards Department, Piscataway, N.J. (hereinafter the “IEEE 802.11 Standard”). Various iterations of the 802.11 standard (e.g., 802.11b) define protocols for different data rates and capabilities. The term 802.11 is intended to cover the entire family of such specifications. The IEEE 802.11 Standard permits either infrared or RF communications, a medium access technique similar to carrier sense multiple access/collision avoidance (CSMA/CA), a power-save mode particularly important for battery-operated mobile units, seamless roaming in a full cellular network, high throughput operation, diverse antennae systems designed to eliminate “dead spots,” and an easy interface to existing network infrastructures.
The basic specifications for the communication of audio, video and multimedia that are applicable to the networks pertaining to the present invention are set forth in the International Telecommunications Union Telecommunication Standards Section (ITU-T) standards H.321-323. The H.321 recommendation relates to asynchronous transfer mode (ATM) channels, H.322 to guaranteed Quality of Service LANs, and H.323 to packet based systems. Other exemplary protocols include session initiation protocol (SIP), Megaco, multimedia gateway control protocol (MGCP), and other proprietary protocols.
In VOIP systems data packets are created from a compressed data stream of digital voice samples. The data packets are formatted for transmission over a data network. Since network latency and packet transmission delays can hamper to the intelligibility and quality of real-time phone conversations, a variety of approaches of giving priority for voice packets (or other real-time multimedia packets) over data packets in the network have been proposed, thus allowing delay-sensitive packets to supercede data packets across any network node in any traffic situation. The H.323 recommendation also provides for call establishment and control, including determining the sequencing and timing of establishing and disconnect procedures, as well as the control of the H.323 session after it is established.
To the extent the Internet Protocol or “IP” (as set forth in IETF RFC 791) is used as the network layer protocol, the recommendations of the International Multimedia Teleconferencing Consortium's Voice over IP Forum may also be applicable to such a Voice over IP (VOIP) network. In a VOIP network, the voice signal is digitized, encapsulated into IP packets, and then routed between VOIP capable devices in an IP network. These packets of voice may then be delivered in real time as voice communications, or stored as voice mail.
Communications between a local area network (LAN) and a wide area network or telephone network are generally performed by communications controller known as a gateway or proxy. In the H.323 standard, for example, a gateway generally refers to an endpoint which provides for real-time, two-way communications between H.323 terminals on an IP network and other ITU terminals, telephones on a PSTN or PBX, and terminals on other networks.
For a mobile device to communicate through a gateway to a PBX system, it must be configured with the commands that the PBX expects to receive to access its functions. One problem associated with connecting a mobile device to a PBX lies in the various PBX systems and their differing internal protocols. It is not uncommon for a single business to have more than one type of PBX system installed. Hence, a device configured to interface with a particular type of PBX will not operate properly if it is connected to a network using a different PBX protocol. This problem is compounded in a wireless environment, where it is not uncommon for a user to move locations and interface with different wireless access points or gateways in the facility depending on which access point is handling the user's calls. If a user roams from one access point to another, the mobile device may cease to operate properly as it no longer knows the proper PBX commands.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.